// Protocol Buffers - Google's data interchange format
// Copyright 2008 Google Inc.  All rights reserved.
// https://developers.google.com/protocol-buffers/
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
//     * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

package com.google.protobuf;

import static com.google.protobuf.Internal.checkNotNull;

import com.google.protobuf.Internal.EnumLite;

import java.util.Arrays;
import java.util.Collections;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Set;

/**
 * Internal representation of map fields in generated lite-runtime messages.
 *
 * <p>This class is a protobuf implementation detail. Users shouldn't use this class directly.
 */
public final class MapFieldLite<K, V> extends LinkedHashMap<K, V> {

    private boolean isMutable;

    private MapFieldLite() {
        this.isMutable = true;
    }

    private MapFieldLite(Map<K, V> mapData) {
        super(mapData);
        this.isMutable = true;
    }

    @SuppressWarnings({"rawtypes", "unchecked"})
    private static final MapFieldLite EMPTY_MAP_FIELD = new MapFieldLite<>();

    static {
        EMPTY_MAP_FIELD.makeImmutable();
    }

    /**
     * Returns a singleton immutable empty MapFieldLite instance.
     */
    @SuppressWarnings({"unchecked", "cast"})
    public static <K, V> MapFieldLite<K, V> emptyMapField() {
        return (MapFieldLite<K, V>) EMPTY_MAP_FIELD;
    }

    public void mergeFrom(MapFieldLite<K, V> other) {
        ensureMutable();
        if (!other.isEmpty()) {
            putAll(other);
        }
    }

    @SuppressWarnings({"unchecked", "cast"})
    @Override
    public Set<Map.Entry<K, V>> entrySet() {
        return isEmpty() ? Collections.<Map.Entry<K, V>>emptySet() : super.entrySet();
    }

    @Override
    public void clear() {
        ensureMutable();
        super.clear();
    }

    @Override
    public V put(K key, V value) {
        ensureMutable();
        checkNotNull(key);

        checkNotNull(value);
        return super.put(key, value);
    }

    public V put(Map.Entry<K, V> entry) {
        return put(entry.getKey(), entry.getValue());
    }

    @Override
    public void putAll(Map<? extends K, ? extends V> m) {
        ensureMutable();
        checkForNullKeysAndValues(m);
        super.putAll(m);
    }

    @Override
    public V remove(Object key) {
        ensureMutable();
        return super.remove(key);
    }

    private static void checkForNullKeysAndValues(Map<?, ?> m) {
        for (Object key : m.keySet()) {
            checkNotNull(key);
            checkNotNull(m.get(key));
        }
    }

    private static boolean equals(Object a, Object b) {
        if (a instanceof byte[] && b instanceof byte[]) {
            return Arrays.equals((byte[]) a, (byte[]) b);
        }
        return a.equals(b);
    }

    /**
     * Checks whether two {@link Map}s are equal. We don't use the default equals method of {@link
     * Map} because it compares by identity not by content for byte arrays.
     */
    static <K, V> boolean equals(Map<K, V> a, Map<K, V> b) {
        if (a == b) {
            return true;
        }
        if (a.size() != b.size()) {
            return false;
        }
        for (Map.Entry<K, V> entry : a.entrySet()) {
            if (!b.containsKey(entry.getKey())) {
                return false;
            }
            if (!equals(entry.getValue(), b.get(entry.getKey()))) {
                return false;
            }
        }
        return true;
    }

    /**
     * Checks whether two map fields are equal.
     */
    @SuppressWarnings("unchecked")
    @Override
    public boolean equals(Object object) {
        return (object instanceof Map) && equals(this, (Map<K, V>) object);
    }

    private static int calculateHashCodeForObject(Object a) {
        if (a instanceof byte[]) {
            return Internal.hashCode((byte[]) a);
        }
        // Enums should be stored as integers internally.
        if (a instanceof EnumLite) {
            throw new UnsupportedOperationException();
        }
        return a.hashCode();
    }

    /**
     * Calculates the hash code for a {@link Map}. We don't use the default hash code method of {@link
     * Map} because for byte arrays and protobuf enums it use {@link Object#hashCode()}.
     */
    static <K, V> int calculateHashCodeForMap(Map<K, V> a) {
        int result = 0;
        for (Map.Entry<K, V> entry : a.entrySet()) {
            result +=
                    calculateHashCodeForObject(entry.getKey()) ^ calculateHashCodeForObject(entry.getValue());
        }
        return result;
    }

    @Override
    public int hashCode() {
        return calculateHashCodeForMap(this);
    }

    private static Object copy(Object object) {
        if (object instanceof byte[]) {
            byte[] data = (byte[]) object;
            return Arrays.copyOf(data, data.length);
        }
        return object;
    }

    /**
     * Makes a deep copy of a {@link Map}. Immutable objects in the map will be shared (e.g.,
     * integers, strings, immutable messages) and mutable ones will have a copy (e.g., byte arrays,
     * mutable messages).
     */
    @SuppressWarnings("unchecked")
    static <K, V> Map<K, V> copy(Map<K, V> map) {
        Map<K, V> result = new LinkedHashMap<K, V>();
        for (Map.Entry<K, V> entry : map.entrySet()) {
            result.put(entry.getKey(), (V) copy(entry.getValue()));
        }
        return result;
    }

    /**
     * Returns a deep copy of this map field.
     */
    public MapFieldLite<K, V> mutableCopy() {
        return isEmpty() ? new MapFieldLite<K, V>() : new MapFieldLite<K, V>(this);
    }

    /**
     * Makes this field immutable. All subsequent modifications will throw an {@link
     * UnsupportedOperationException}.
     */
    public void makeImmutable() {
        isMutable = false;
    }

    /**
     * Returns whether this field can be modified.
     */
    public boolean isMutable() {
        return isMutable;
    }

    private void ensureMutable() {
        if (!isMutable()) {
            throw new UnsupportedOperationException();
        }
    }
}
